If Ubiq is very good then why coingeko display developer interest % is only 13 ? why it is less if this one is same as ETH ?

Well, for one it appears they're only looking at the go-ubiq repository which isn't the entirety of the project. And for two, it's maintained by a small group of developers because it's a no ico / no pre-mine coin. The code is solid, and great help is provided in slack which means less issue closure and PR resolutions, which appear to be other metrics that factor into that score.

For coins like ETH it's easy for them to just pay off developers because they have a huge pile of cash from the ICO. The devs work crypto-related jobs, and had been maintaining the predecessor coin JBS for over 3 years. Not only did this coin have unique features at the time, it was the most stable proof of stake coin I've ever used. That was part of what got me interested in the project.

So yea, base on the algorithm I could see it getting a less than satisfactory dev score, but 13 doesn't seem fair in my opinion.

If Ubiq is very good then why coingeko display developer interest % is only 13 ? why it is less if this one is same as ETH ?

It is subjective and you can't expect the CoinGecko staff to be monitoring every single coin closely, nor spending time chatting with devs. I would take their dev interest rating with a large grain of salt.